Electrode and envelope assembly for multielectrode space discharge devices



Oct. 23, 1951 H. R. JACOBUS, JR, ETAL 2,572,032

' ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE SPACE DISCHARGEDEVICES Filed Jan 26, 1949 2 SHEETSSHEET 2 IJYVENTOR.

Patented Oct. 23, 1951 ELECTRODE AND ENVELOPE ASSEMBLY FORMULTIELECTRODE SPACE DISCHARGE DEVICES Herbert R. J acobus, J L, WhitePlains, and Harold L. Lipschultz, New York, N. Y., assignors to SonotoneCorporation, Elmsford, N. Y., a corporation of New York ApplicationJanuary 26, 1949, Serial No. 72,986

7 Claims.

This invention relates to electron space charge devices in which anelectrode assembly comprising an anode, a cathode and at least one gridor control electrode interposed between the cathode and the anode, areenclosed in a hermetically sealed envelope, and more particularly tosuch electron discharge devices which are known commercially assubminiature electron tubes, although some of the features of theinvention are applicable to electron space discharge tubes other thansubminiature tubes.

Among the objects of the invention are subminiature tubes embodyingnovel features which make it possible to materially reduce their overallvolume and to simplify the critical problems connected with theirmanufacture and to make it possible to manufacture such tubes on a massproduction basis with a high degree of uniformity of their operatingcharacteristics.

The foregoing and other objects of the invention will be best understoodfrom the following description of exemplifications thereof, referencebeing had to the accompanying drawings, wherein:

Fig. l is a vertical cross-sectional View of one form of amulti-electrode subminiature tube exemplifying the invention, the tubebeing shown in a scale of about 1 to 8;

Fig. 2 is a cross-sectional view of the tube along line 2-2 of Fig. 1;

Fig. 3 is a vertical cross-sectional and partially elevational view ofthe same tube along line 33 of Fig. 2; 7

Figs. 4 and 5 are cross-sectional views along lines 4-4 and 55 of Fig.3, respectively;

Figs. 6 and 7 are detail cross-sectional views of the upper and lowerparts of the tube along lines 6-6 of Fig. 4 and lines 'I-'I of Fig. 5,respectively;

Figs. 8 and 9 are perspective views of the electrode assembly of a tubesimilar to that of Figs. 1 to 7, as seen from the top and bottom,respectively, with a modified anode arrangement, parts of the envelopeand of the electrodes being broken away;

Figs. 10 and 11 are elevational and plan views of the anode structure ofthe tube shown in Figs. 1 to '7; and

Figs. 12 and 13 are elevational and plan views of the auxiliaryelectrode of the tube shown in Figs. 1 to 7.

There are many applications requiring multielectrode electron amplifiertubes of the subminiature type, having extremely small dimensions andable to operate with a high degree of efiiciency andwith uniformdesirable operating characteristics. Among such applications arehearing-aid amplifiers, proximity fuses, and radio broadcast receiversof a miniature size suitable for hidden wear in the pocket of the user,and other applications in which a minimum of space is a critical factor.ciples of the invention are applicable to other types of subminiaturetubes, and some aspects of the invention are of a broader scope, theirapplication will be described in connection with a pentode-type tubeshown in Figs. 1 through 13, which has a very wide use as a voltage gainand power amplifier.

The tube shown comprises an evacuated, generally elongated tubularenvelope II of vitreous material such as glass, which encloses anelectrode assembly generally designated I2, having a plurality ofelectrodes which are connected to a plurality of leads I3, I4, I5, I6and I1, her- .metically sealed through an electrically insulatedterminal end wall portion I8 of the envelope to provide external circuitconnections to the electrodes. The terminal end wall portion I8 is madein the form of a wafer-like stem of Vitreous material sealed aroundportions of lead conductors I3 to I! held generally aligned in a planevertical to the plane of the stem. The wafer-like lead stem I8 extendsin a direction transverse to the envelope and is fused to its lower endborder.

The electrode assembly comprises a filamentary cathode 2|, a controlgrid 22, a screen grid 23, and an anode 24, all extending longitudinallygenerally parallel to a common axis of the electrode assembly, and anadditional auxiliary electrode structure having two auxiliary electrodesor electrode sections 25, 25, interposed across the electron pathbetween the anode 24 and the screen grid 23. In the tube shown, thefilamentary cathode 2| is made of a thin filament of a refractory metalsuch as tungsten, provided with an oxide coating which emits electronswhen the filament is heated to an elevated temperature. The two oppositeends of the filamentary cathode'ZI are provided with mounting portionsin the form of metal strips or tabs Although the prin-- v 2'! to whichthe ends of the filament are secured as by welding, and which are inturn secured to cathode supports which support the filamentary cathodein its proper operative position.

The two grids 22, 23 are made of very fine refractory metal wire, forinstance, tungsten wire about .001" and .0015 in diameter, the innergrid 22 being wound as a helix on and secured to two inner side rods orgrid posts '28, and the outer grid 23 being similarly wound andsupported on two outer side rods or grid posts '23. The grid pests ofsuch subminiature tubes are usually formed of thin Wires, for instance,the inner grid posts of wire about .015" diameter, and the outer gridposts of, wire. about .020" di ameter.

The grid posts as well as the cathode 2 anode 24 and the two auxiliaryelectrodes 28 of the electrode assembly are held in their operativeposition by two similar generally fiat sheet-like insulating spacerelements 33, 32, made of a material having a high dielectric constant.The two sheet-like spacers 3f, 32 are provided. with apertures oropenings engaged by junction or supporting ends of the grid posts and ofthe other electrodes which are joined'by the spacers into aself-supporting electrode assembly.

The anode 2A is made of sheet metal, and is arranged to receive theelectrons emitted by the cathode filament under the controlof thecontrol electrode, in a manner well known in the art. In all priorsubminiature tubes the anode was held in its properly spaced operativeposition relatively to the other electrodes of the electrode assembly byjunction portions or supporting rods seated in openings of theinsulating spacers. Since the anode structure of such tubes forms theoutermost part of the electrode assembly, the insulating supportingspacers on which the opposite ends of the anode supporting rods areretained, had to be made of sufficient width to serve as an anchoragenot only for the grid posts but also for the junction elements of theanode.

According to one phase of the invention, a material reduction of thewidth and the over-all volume of the electrode assembly-a criticalfactor in subminiature tubes-is made possible by providing the exposedperipheral edge regions of the two insulating spacers 3!, 32 with spacedretainer recesses 33, and by forming the opposite boundary edges of theanode sheet structure 24 with a plurality of spaced sheet tongueportions interlockingly engaging and interfitting with the retainerrecesses of the two spacer members, so as to secure the two spacers 31,32 to the unitary tubular anode sheet structure and join. them into aself-supporting assembly structure.

As shown in Figs. 1 to 9, and in detail in Figs. and 11, the anode 24 ismade in the form of a cylindrical tubular sheet structure of thinrefractory metal, such as nickel. Each of the opposite generallycircular boundary edges of the anode 24 has two spaced sheet ears ortongues 34, 35, interlockingly engaging and interfitting with the twospaced retainer recesses 33 of the two opposite spacer members SI, 32,so as to secure the two spacers 3|, 32 to the upper and lower ends ofthe tubular anode 24 and join them into a self-supporting assembly.

The junction tongues 34, 35 of the anode are provided with intermediateshoulder portions 36 against which the two spacers 3|, 32 abut when theyare joined to. the anode structure, to provide annular gap spacesbetween the major part .of

the circular boundary edges of the anode 2.4 an

the facing portions of the mica spacers 3|, 32, and limit to a minimumthe area along which they make direct contact with the metallic anode.

As is well known, as a part of the evacuation process, the metallicanode structure has to be heated to a high temperature of about 900 C.,in order to de-gas it. On the other hand, the mica insulating spacerscomprise hydrates which decompose when heated to an excessivetemperature, weakening the spacer sheet structure and reducing itsresistance to electric leakage, a phenomenon known as puffed mica. Bylimiting the contact area between the relatively large anodesheet,structure and the mica insulating spacers joined thereto to the smalledge surface portions of the junction tongues of the tubular anode andthe recess edge-regions of the spacers, the flow of heat from the anodemaintained at a high temperature to the spacer body, is kept down, anddamage to the mechanical and insulating characteristics of theinsulating spacers 3!, 32 is avoided.

The annular gap spaces between the circular boundary edges of the anode24 and the insulating spacers 3!, 32 provide windows through which theinterior elements of the electrode assembly enclosed by the anode, andtheir proper mounting and spacing, may be illuminated and visuallyinspected.

The interlocking engagement of the anode junction tongues 34, 35 withthe peripheral retainer recesses 33 of the two spacers 3|, 32 provides agood mechanical interconnection there between and joins them into aself-supporting mechanical structure, provided the anode tongue portions34, 35 are slightly bent in inward direction after the two spacers 3|,32 have been fitted with their recesses over the tongues againstthetongue shoulders 36. It is not necessary to bend the end portions of theanode tongues 34, 35 over the outer surfaces of the spacers in order toprovide such good operative mechanical interconnection between the anodeand the two spacer elements so supported thereon.

As shown in Figs. 1 to 9, to provide a stronger interconnection betweenthe anode 24 and the two spacers 3!, 32, both anode tongues or only oneanode tongue, such as tongue 34, of each boundary edge of the anode, maybe bent as much as about against the outer surface of the respectiveadjoining spacer members 3!, 32, without bringing the tongue portionoverlying the spacer into direct contact engagement therewith.

As shown in Figs. 8 and 9, to decrease the area of heat transmissionbetween the metallic anode structure, which has to be heated to ahigh-degassing temperature, and the insulating spacers 31,32, the anodejunction tongues 34, 35 may be slit along their length into two tonguesections 51, 58, one slit narrow tongue section 51 of each slit beingbent over the outer surface of the recess edge region 33 of therespective spacers 31!, 32 engaged thereby, the other narrowtongue-section 58' projecting outwardly away from the spacer surface.This arrangement'assures that the two spacers are held in engagementalong their relatively long recessed edges with a relatively longabutting region of the junction tongues engaging the edge recesses 33while only a narrow part of the width of the metallic junction tongues34, 35 of the anode is bent over the outer surface of the respectiveinsulating anode spacers 3 I, 32 to provide strong mechanical retainerelements retaining the two spacers in their interlocked engagement withthe tubular anode structure.

As shown in Figs. 1 to 5, each of the insulating sheet spacers 3|, 32 isalso provided with resiliently yieldable spacer projections 39 which areshaped to engage the inner surface of the tubular envelope H and serveto maintain the anode and the entire electrode assembly in the properlyspaced and aligned position within the envelope when the electrodeassembly is inserted into the envelope from the bottom end thereofbefore the stem portion l8 thereof with the leads sealed therein isproperly joined and sealed to the side walls of the envelope.

In the tube of the invention, an auxiliary elec trode structure formedof the two auxiliary elec trodes 25, 26 of sheet metal, is utilized as ashielding or suppressor electrode for shielding the electron dischargespace against secondary electron emission from the anode, and for givingthe tube the desired operating characteristics.

As shown in Figs. 1 to 9, and in detail in Figs.

12 and 13, two auxiliary electrodes 25, 26 are made of elongated stripsof a refractory sheet metal, having at its opposite end edge portionsjunction tongues 31 seated in elongated openings or slits 38 of theopposite insulating spacers 3|, 32 for holding the sheet electrodes 25,26 in their proper operative position within the electrode assembly. Thetwo auxiliary shield electrodes 25, 26 are positioned so that theyprovide wide sheet surfaces which are spaced from the cathode 2| and theanode 24 by about the same distance as the grid posts 29 of the screengrid 23, and which extend transversely across the path of the electronsfrom the cathode 2| across the two grid electrodes 22, 23 towards thefacing arcuate regions of the circular anode 24. Each auxiliary shieldelectrode 25, 26 has a central wall portion 4| having elongated electronbeam openings 42 confining the beam of electrons passing from thecathode to the anode. Each auxiliary shield electrode 25, 26 has twowings or side wall portions 43 bent inwardly toward the region of thegrid posts 29, so that when the two auxiliary electrodes 25, 26 aremaintained at the cathode potential, the fiow of electrons between thecathode 2| and the anode 24 will be confined to the two beam openings 42of the opposite auxiliary electrodes 25, 26. Since the manner in whichsuch auxiliary electron-intercepting electrodes operate is well known inthe art-as described, for instance, in the U. S. Patents to Schade,2,107,520; Strutt 2,205,500; and Shoenberg 2,113,801; and in the BritishPatent No. 324,175-no further description of their operation isrequired. When used in space charge tubes operating as gain and poweramplifier tubes, such auxiliary electrodes 25, 26 of the tube of theinvention shown, are connected to the opposite ends of the filamentarycathode 2| and maintained at the cathode potential.

In the tube shown, the two insulating spacers 3|, 32 of the electrodeassembly have in addition to the slit openings 38 for the junctiontongues 31 of the auxiliary electrodes and the openings for seating thejunction ends of the two sets of grid rods 28, 29, a generally centralopening 44 of triangular shape to provide at the vertex of two angularedges thereof a positive seat against which spaced seating portions ofthe cathode filament are held seated and positioned in proper spacingrelatively to the other electrodes.

For satisfactory operation of such discharge tubes, it is essential thatthe efiective portion of the filamentary cathode 2| facing the operativeportions of the other electrodes shall be held stretched under tensionin a predetermined desired operative position. Because of the closeelectrode spacing, the problem of connecting the opposite ends of thethin filamentary cathode to proper tensioning supports which hold thecathode filament tensioned and biased against the angular positioningrecesses of the two spacers, is critical, particularly if such tubes areto be manufactured at low cost on a mass production basis.

.The required tiny connector elements by means of which the oppositeends of the filamentary cathode are connected and held tensioned in theoperative position to the electrode assembly, are so arranged as to makeit possible to readily align the connector elements with junctionelements of the filamentary cathode and of the cooperating supportingparts of the electrode assembly, and to readily join the alignedelements in positions in which they automatically operate to maintainthe cathode in the desired operative tensioned condition.

As shown in Figs. 1, 2, '1 and 9, the lower mounting tab 21 of thefilamentary cathode 2| is supported in its operative position by agenerally L-shaped metallic connector strip 46 having one relativelylong arm to which the mounting tab 21 of the filamentary cathode 2| issecured as by welding. The connector strip 46 has a shorter arm 41angularly bent relatively to its longer arm and secured to the lowerjunction tongue 31 of the auxiliary electrode 25 projecting beyond theouter side of the lower spacer 32. The width of the connector strip arm41 is substantially equal to the width of the projecting junction tongue31 of the sheet electrode 25 to which it is secured, thereby enablingthe operator to place them in aligned overlapped positions in which theyare secured, as by welding. This connector strip arrangement obviatesthe necessity for using judgment and care when securing the connectorstrip 46 in its proper operating position to the junction tongue 31 bymeans of which it is supported on the outer side of the electrode spacer32.

As seen in Figs. 1, 5 the longer arm of the connector strip 46 to whichthe bottom mounting,tab of the filamentary cathode 2| is secured, ismade of such length that when the filament mounting tab 21 is secured ina position where the edge of the tab 29 is substantiallyaligned with theend edge of the connector strip 46, the latter will automatically biasthe bottom portion of the filamentary cathode 2| into seating engagementwith the vertex of the angular recess of the opening spacer 44 throughwhich it passes.

As seen in Figs. 1 to 9, by mounting the two auxiliary shield electrodes25, 26 so that they extend between the narrow sides of the generallyfiat or oblong grid electrodes 22, 23, in the manner shown, the bottomjunction tongue 31 of the auxiliary shield electrode 26 which serves asa support for the cathode connector strip 46 provides for a relativelylong connector spring arm extending in a direction generallyperpendicular to the desired direction of the biasing seating forceswhich are exerted by it on the end portion of the filamentary cathode 2|connected thereto. With this arrangement of the auxiliary sheetelectrodes 25, 26, the L-shaped connector strip 46 connecting thejunction tongue 31 of sheet electrode 26 to the cathode tab 21 of thecathode 2| provides a relatively long elastic biasing arm exerting thedesired cathode biasing forces: in the direction perpendicular to thedirection of its length.

:The generally L-shaped structure given to the cathode connector strip45, 51, as seen in Figs. 1., Sand 9, facilitates not only readyalignment of its ends with respect to the elements to which they have tobe connected, but also greatly simplifies the problem of welding itsshort arm 41 to its supporting junction tongue 37. To perform suchwelding operation, one of the welding electrodes may be placed againstthe inner surface of the bottom junction element 31 of the auxiliarysheet electrode 25 through the gap space between the longer arm 48 ofthe connector strip and the outer surface of the spacer 32, while theother welding electrode is placed against the outer surface of the shortconnector strip arm 4'! held against the junction element 3?, in whichposition the welding current is passed between the welding electrodes.

As shown in Figs. 1, 3, 4, 6 and 8, the upper end of the filamentarycathode 2| is held tensioned and biased against the angular cornerrecess of the central opening 44 of the upper insulating spacer 3| by atensioning connector structure including a reversely bent generallyU-shaped connector rod 5| and a coil spring 52. One arm of the metallicU-shaped connector rod 5| is aihxed, as by welding, to the outwardlyprojecting junction tongue 31 of the auxiliary sheet electrode 25. Thecoil spring 52 comprises a plurality of helical turns coiled looselyaround the freearm of the connector rod 5|, and has one spring end arm53 restrained from movement by affixing it as by welding to a portion ofthe lower arm of rod 5|. The other end of the loose coil spring 52terminates in a substantially straight relatively long spring arm 54 tothe end region of which is secured as by welding, the upper mounting tab21 of the cathode filament 2|. The supporting rod member 5| is heldaligned in the direction of its length by the tongue portion 3'5 of thesheet electrode 25 to which it is secured in a direction generallyparallel to the direction of the biasing forces which the free springarm 45 has toexert on the upper end of the filamentary cathode 2 forholding it biased against the corner recess of the supporting opening 3!of the top spacer 3|.

Because of this arrangement, the coiled spring tensioning support member52 of the cathode support may be readily placed in its operativeposition on the U-shaped rod member 5! and secured thereto in its properoperative position in which its free spring arm 54 exerts the desiredelastic and biasing tensioning forces on the cathode filament afiixedthereto. This arrangement facilitates the securing of the U-shaped rodmember 5! of the cathode tensioning spring coil 52 in its proper alignedmounting position by merely aligning its lower arm against theprojecting sheet tongue 3'| of the auxiliary sheet electrode 26 andwelding them to each other by a simple welding operation. With theUshaped rod member 5| so secured in its aligned operating position, itsfreely projecting other arm is ready to receive and hold the coil spring52 in a position in which its free cathode tensioning arm 54 willautomatically exert on the top end of the filamentary cathode 2| securedthereto, the desired tensioning and biasing forces which cause thefilament portion passing through the upper cathode opening 44 of thespacer 3| to be moved along the angular recess edges to the cornerseating recess and: supportingit therein in 'proper operative tensionedposition.

The arrangement of the connector rod 5| with its coil spring 52 shown,makes it possible for the operator to secure the U-shaped mounting rodof the cathode tensioning coil spring 52 in the properly alignedposition by merely aligning the end of the lower inward arm of theU-shaped supporting rod 5| with the edge of outwardly projectingjunction'tongue 37 of the auxiliary sheet electrode ZS-with the inwardrod arm extending substantially parallel to the adjacent outer surfaceof the spacer 3 |and to apply welding electrodes to the exposed surfacesof the overlapping portions of the tongue member 31 and the inward rodarm for welding them in the aligned position in which the free arm ofthe supporting rod will provide the proper aligning support for the coilspring 5|, in which position its free straight spring arm 54 exerts thedesired cathode positioning and tensioning forces on the cathodefilament 2|.

In Figs. 1 and 5 the inward arm of the U-shaped cathode mounting coilspring 52 is shown affixed to the outwardly projecting tongue portion 37of the auxiliary sheet member 25 in a position in which the lower arm ofthe rod member 5! is substantially in direct engagement with the outersurface portion of the insulating spacer 3| bordering the openingthrough which the tongue 37. projects. With such arrangement, the lowerarm of the mounting rod 5| operates to retain the spacer 3| and preventaxial displacement thereof. Such connection of the U shaped springmounting rod 5| also facilitates alignment and positioning of themounting rod 5| relatively to the sheet tongue 31 to which it has to besecured in order to provide a properly aligned mounting support for thecoil spring 52.

However, to provide the desired aligned assembly it is sufficient toalign the end of the inward arm of the mounting member 5| with the edgeof the sheet tongue 31 to which it is to be secured, in a position inwhich the inward arm of the mounting rod 5| is placed at some smalldistance from the insulating spacer 3| substantially parallel to theplane of the spacer, as this will, by itself, automatically assure thatthe free arms of the U-shaped spring mounting rod 5| will provide theproper aligned mounting support for the cathode tensioning coil spring52.

As shown in Figs. 1, 3, 6 and 13, the upper junction tongues 35 of thetubular anode 25 has secured thereto a getter support in the form of ametal strip 6| extending generally parallel above the outer surface ofthe upper insulating spacer 3|. The getter support strip 6| has formedtherein a pocket 62 with an opening facing the adjacent side wallportion of the envelope and a body of getter material held affixedwithin the pocket.

' The getter support strip 6| is bent to generally conform to thetubular shape of the envelope, and has a central portion provided withthe getter pocket 62 and two arms or wings extending therefrom so as toconstitute barriers which confine evaporated vapors of the gettermaterial to the region of the envelope facing the outer surface of thegetter support BI and substantially prevent getter vapor from materiallyreducing the surface leakage resistance of the insulating spacer 3|adjacent to which it extends.

To keep the height and size of the tube structure to a minimum,'thegetter support strip BI is arranged'to constitute in effect a. shortoutward extension of an arcuate portion of the cylindrical anodestructure. With such arrangement, the getter structure doe not increasethe size of the electrode structure, since it occupies the regionimmediately above the outer surface of the upper insulating spacer whichhas substantially the same height as the region in which the cathodetensioning support elements 51, 52 are positioned.

Qne side wing of the generally arcuate getter support forms a junctionportion 63 thereof,

which is secured as by welding to the anode junc- 'tion tongue 35. Thejunction portion 63 of the getter support strip BI is secured to theoutwardly projecting tongue portion 35 of the anode in a position inwhich an edge of the junction portion 63 substantially engages theadjacent surface portion of the insulating spacer 3|, so as to retainthe spacer 3| against displacement in axial direction away from theseating shoulder portion 38 of the tongue 35.

In order to prevent overheating of the insulating body of the spacer 3!when the getter strip BI is heated to the high temperature at which thegetter body evaporates, the edge portion of the getter support strip 6|extending beyond its junction portion 63 is spaced by a small gap fromthe adjacent surface portion of the insulating spacer 3|, in the mannerindicated in Figs. 1 and 3.

By the arrangement shown, the getter support with its getter is confinedto' a short region of the height of the tube substantially coextensivein height with the region in which the cathode tensioning supportingelements are confined, thus making it possible to reduce the over-alllength or height of the tube to that occupied by the actual elements ofthe electrode assembly.

As shown in Figs. 1, 3, 6, and 9, the inward end portions of theconductor leads l3 to H are shaped by bending and are displaced from theplane in which they sealed through the fiat stem 8 of the envelope, sothat the inner end portions of the several leads terminate substantiallyin a plane transverse to the tube axis, and engage outwardly projectingjunction elements of the several electrodes to which they are secured bywelding, as well as the outer surface of the bottom insulating spacer 32of the electrode assembly. This arrangement of the electrode leadsassures that when joining the stem 8 to the adjacent walls of theenvelope, the stem is automatically aligned coaxially with andsubstantially parallel to the plane of the insulating spacer 32 of theelectrode assembly at the desired proper minimum distance therefrom.

In the tube shown, the inner end of lead I3 is connected by a metallicconnector strip 64 welded thereto, to the downwardly projecting junctiontongue 37 of the auxiliary sheet electrode 26, which also serves as aterminal connection to the upper end of the filamentary cathode 2|. Theinner end of lead [4 is secured as by welding to the outwardlyprojecting junction end of the grid rod 32 of the control grid 22. Theinner end of the lead conductor 15 is secured as by welding to theadjacent downward junction tongue 31 of the other auxiliary sheetelectrode 25 which also serves as the terminal connection for the lowerend of the filamentary cathode 2|. The inner ends of leads [6 and l! aresecured by welding to the adjacent junction end of grid post rod 29 ofthe outer grid 23 and to the downwardly projecting junction tongue 35 ofthe anode 24, respectively, thereby providing lead connections to thescreen grid and to the anode.

Bysecuring several of the electrode leads 13 to the insulating spacers3!, 32, and correspond- H, which are displaced from a plane, to theelectrode assembly so that their inward ends also engage the adjacentouter surface portions of the spacer 32, they also serve as retainerswhich retain the lower spacer 31 against axial displacement relativelyto the electrode assembly.

In such subminiature tubes, the close, critical spacing between thecylindrical anode 24 and the two auxiliary sheet electrodes 25, '26 withtheir electron beam defining openings 42 relatively to each other and tothe other electrodes of the electrode assembly, makes it essential toassure that their relative shape and spacing is not disturbed when thejunction tongue portions of the electrode sheet members 24, 25 and 26arebent or subjected to strains while joining them into the electrodeassembly described above, or through the forces exerted thereon by theconnector elements joined thereto, such as the cathode biasing andsupporting connector elements 46, 5|, 52, joined to the tongue junctionportions of the two auxiliary sheet electrodes 25, 26.

In accordancewith one phase of the invention, the cylindrical tubularanode structure 24 is provided, at two spaced portions of its lengthadjacent the end regions thereof, with arcuate channel formations 55extending in a direction transverse to its axial length, so as tomaterially increase the stiffness of the anode structure againstdeformation of its cylindrical shape when the tongue junction portions34 thereof are bent in the procedure of joining the two insulatedspacers 3|, 32 to the opposite ends of the anode structure.

Furthermore, in accordance with a phase of the invention, the two sidewall portions 43 of each of the auxiliary sheet electrodes 25, 26 areprovided with an elongated channel formation 48 generally parallel totheir axial length for materially increasing their stiffness andsubstantially preventing disturbing deformations thereof and of theirbeam openings by bending or other forces applied to theirjunctiontongues 31.

In order to enable those skilled in the art to readily practice theinvention, and without in any way limiting its scope, there are givenbelow data for a tube of the invention, which proved highly satisfactorywhen used as a gain amplifier:

The insulating mica spacers 3|, 32 are about .006" to .010 thick, andare .220" in diameter, and are spaced by a distance of .315". The centerdistance between the outer grid posts is 1125. The center distancebetween the inner grid posts is .065. The distance between the mountingslits of the auxiliary sheet electrodes is .120".

The cylindrical anode is of nickel or stainless steel sheet material,.005" thick and is .188" in diameter.

The auxiliary sheet electrode is made of nickel or stainless steel sheetmaterial .007 thick, their width is .143", and their beam opening is.25" by .062".

The getter support is .093 high.

The cylindrical glass envelope has an inner diameter of .251", anoutside diameter of 5, and a length slightly more than A".

The tube may be designed for operation with a filament current of 20milliamperes, 15 milliamperes, or 10 milliamperes, with a voltage of.065 volt across the filament. When operating with a plate voltage and ascreen voltage of 22.5 volts, and a plate current of 200 microamperes,it has a transductance of micromhos and a plate resistance of 1 megohm.

Similar tubes with a distance of .600" between inglylonger electrodes,will serve as a power tube. With the filament designed for operationwith a filament voltage of 1.25 volts and a filament current of .020ampere, such power tube operating with a plate voltage and screenvoltage of 22.5 volts and a control grid voltage of volts, and a platecurrent of 500 microamperes, has a transductance of 400 micromhos, and apate resistance of 170,000 ohms. It has a power ou.put of 4.0 milliwattsat 12% distortion.

The subminiature tube of the invention of the type described, may bereadily manufactured by the following procedure:

The upper insulating mica spacer 3| is placed with its top surface on anupwardly facing assembly jig with its inner sunace facing upwardly. Thejunction ends of the two grid posts 28, 29 of the inner grid 22 and theouter grid 23, respectively, are then inserted into the correspondingopenings of spacer 3|. The junction tongues 3'! 0f the two auxiliarysuppressor sheet electrodes 25, 26 are then inserted into the junctionslit 38 The bottom spacer 32 is then positioned above the so-assembledelectrodes 22, 213, 24, 25, 26, and its openings and recesses areslipped over the bottom junction ends of the grid posts 28, 29, and thebottom junction tongues 37 and 34, of the suppressor electrodes 25, 26and of the anode 24, respectively. With the several electrodes and thetwo spacers held in inverted position on the assembly jig, the anodejunction tongue 34 is bent about 90 over the outer surface of the bottommica spacer, and the other anode tongue is temporarily bent slightlyinwardly, thereby assuring that the bottom spacer 32 will be retained inits assembled position on the cylindrical anode (Figs. 4 and 14).

The electrode assembly is then turned 180 to bring the top spacer 3| toa position in which it faces upwardly. The upper anode junction tongue34 is then bent about 90 over the outer surface of the spacer 3|, andthe other anode junction tongue 35 is temporarily slightly tiltedinwardly to assure that the upper spacer 3| is retained on thecylindrical anode 24 (Figs. 3, 13). In addition, the top junction tongue3'! of the suppressor electrode 25 is slightly tilted in inwarddirection to assure that it does not make contact with the getter pocket62 of the getter support 5| when the latter is secured to the assembly(Figs. 1, 2, 13)

After removing the electrode assembly from the assembly jig, theL-shaped cathode connector strip 43 is placed with its junction arm 41in overlapping alignment against the coex tensive bottom junction tongue37 of the suppressor electrode 25, and secured thereto by welding. TheU-shaped spring-mounting rod 5| of the cathode tensioning coil spring 52is placed in the aligned position shownwith its two arms aligned in theplane of the top tongue 31 of the suppressor electrode 26 and extendingparallel to the plane of the spacer 3 |and with the inner arm of the rod5| overlappingl aligned with one edge of the screen tongue 31 securedthereto by welding, so that the upper free arm of rod 5| extendsgenerally parallel to the plane of the biasing forces exerted by thefree spring arm 54 on the cathode filament 2|.

In a separate sub-assembly operation, the upper mounting tab 27 of thecathode 2| is secured in aligned position to an end portion of thefreespring arm 54 in a direction generally perpendicular thereto, sothat when the spring coil 52 is placed on the free arm of U-shaped rod5|, the free spring arm 54 will exert on the top end of the cathodefilament 2| biasing and tensioning force in the direction of the planedefined by the grid side rods 28, 29.

The filamentary cathode 2| carried freely suspended in a verticalposition by the end portion of the straight spring arm of the coilspring 5| is then dropped or threadedwith its lower and through therelatively large aligned central cathode openings of the two spacers 3|,32 of the electrode assembly. The coiled turns of the coil spring 52 arethen slipped over the free upper arm of the U-shaped mounting rod 5|.The lower cathode mounting tap 2'! is then welded to the end of the freearm of the L-shaped connector strip 43, the other arm of which has beenpreviously secured in aligned overlapping position to the bottom tongue3'! of the suppressor electrode 25. The short spring arm 53 of the coilspring 52 i then gripped and brought against the lower arm of theU-shaped mounting rod 5| and welded thereto in a position in which thefree arm 54 of the coil spring 52 extends substantially above the gridside rod 28, which is next to the angular filament seating recess of thespacer opening 44 (Fig. 3). In this position the free spring arm 54exerts the desired elastic tensioning and biasing forces which maintainthe cathode filament 2| tensioned and biased to come into seatingengagementwith the vertex of the angular recess of the cathode seatopenings 44 of the two spacers 3|, 32.

The end portion 53 of the getter support strip 6| is then placed inoverlapping alignment with the upper anode tongue 35, and weldedthereto, the tongue 35 having been straightened before performing thewelding operation, since the welded end of the getter strip 6| nowserves to retain the spacer 3| against axial displacement.

By the foregoing operations, all the elements of the electrode assemblyincluding the cathode and its tensioning and biasing support, are alljoined and secured to each other into a complete self-supportingelectrode assembly in which substantially all operative parts occupytheir final operative position, in which the proper relationship andspacing of the individual electrode elements may be inspected andchecked.

It will be apparent to those skilled in the art that the novelprinciples of the invention thereof will suggest various othermodifications and applications of the same. It is accordingly desiredthat in construing the breadth of the appended claims they shall not. belimited 'to the specific 'exemplifications of the invention describedabove.

What 'is claimed is:

"1. .In an electron space discharge device: an assembly of electrodesextending longitudinally generally parallel to a common axis, includinga filamentary cathode having a cathode junction end, and a sheetelectrode having at one end a junction tongue; a, generally flatinsulating spacer extending transversely to said axis for spacing theends of said electrodes and having a plurality of spacer openings forreceiving said cathode junction end and said junction tongue; aconnector structure connected between said cathode junction. end andsaid Junction. tongue for tensioning said cathode and exerting seatingforces restraining the cathode junction end against a cathode seatportion of the spacer opening receiving said cathode junction end; saidconnector structure comprising a U-shaped rod having two rod arms and acoil spring loosely held on one rod arm; said coil spring having at itsloose end a spring arm secured to said cathode junction end; the endportion of the other rod arm being secured to said junction tongue in aposition in which the end of said other rod arm is substantially alignedwith the adjacent side edge of the junction tongue, and the two rod armsextend substantially parallel to the surface of the adjacent spacer andto the direction of said seating forces; said spring arm extending froma portion of said coil substantially aligned with the other side edge ofsaid tongue; the other end of said coil spring being secured to saidother rod arm.

2. In an electron space discharge device: an assembly of electrodesextending longitudinally generally parallel to a common axis, includinga filamentary cathode having a cathode junction end, and a, sheetelectrode having at one end a junction tongue; a generally fiatinsulating spacer extending transversely to said axis for spacing theends of said electrodes and having a plurality of spacer openings forreceiving and positioning said cathode junction end and said junctiontongue; a connector strip connected between said cathode junction endand said junction tongue for tensioning said cathode and exertingseating forces restraining the cathode junction end against a cathodeseat portion of the spacer opening receiving said cathode junction end;said connector strip comprising two angularly disposed strip arms, onestrip arm being secured to said cathode junction end, and the otherstrip arm being of a width substantial- 1yequal to the width of saidjunction tongue and being secured thereto in substantially overlappingalignment therewith, and carrying said one strip arm at a distance fromsaid spacer.

3. In an electron space discharge device: an assembly of electrodesextending longitudinally generally parallel to a common axis, includinga filamentary cathode having two opposite junction ends, and two sheetelectrodes each having at its opposite ends a junction tongue; twogenerally fiat insulating spacers each having a plurality of spaceropenings for receiving the cathode junction end and the junction tonguesof said sheet electrodes and spacing the other of said electrodes; aconnector structure at one end of the electrode assembly connectedbetween one cathode junction end and the junction tongue of one sheetelectrode for tensioning said cathode and exerting seating forcesbiasing the adjacent cathode junction end against a cathode seat portionof the spacer opening receiving said cathode junction end, and aconnector strip at the other end of the electrode assembly connectedbetween the other cathode junction end and the junction tongue of theother sheet electrode; said connector structure comprising a U-shapedrod having two rod arms and a coil spring loosely held on one rod arm,said coil spring having at its loose end a spring arm secured to theadjacent cathode junction end; the end portion of the other rod armbeing secured to its junction tongue in a position in which the end ofsaid other rod arm is substantially aligned with the adjacent end of thetongue, and the two rod arms extend substantially parallel to thesurface of the adjacent spacer and to the direction of said seatingforces; said spring arm extending from a portion of the coilsubstantially aligned with the other side edge of the tongue to whichthe rod" is secured; the other end of said coil spring being secured tosaid other rod arm; said connector strip comprising two angularlydisposed arms, one strip arm being secured to the adjacent cathodejunction end and the other strip arm being of a width substantiallyequal to the width of the cooperating junction tongue and being securedthereto in substantially overlapping alignment therewith for carryingsaidone strip arm at a distance from said spacer.

4. In an electron space discharge device: arr assembly of electrodesextending longitudinally generally parallel to a common aXis including atubular anode of sheet metal and at least twoadditional electrodessurrounded by the anode; two spaced generally fiat sheet-like insulatingspacers extending transversely to said axis and holding the oppositeends of said electrodes in; closely spaced operative positions andspaced from each other; each of said spacers having along its exposedperipheral edge at least two spaced retainer recesses each of smalldepth and. relatively large width; each of the opposite ends of saidtubular anode having at least two junction sheet tongues extendingtherefrom and in-- terlinkingly engaging and interfitting the two spacedrecesses of said two spacers for securing said two spacers to said anodeand joining them and said electrodes into a self-supporting electrodeassembly, at least one of said junction tongues at each end of the anodehaving two: separated tongue sections, one tongue. section. beingangularly bent over the spacer surface and? the other tongue sectionextending away there-- from.

5. In a space discharge device as claimed im claim 4, said assembly ofelectrodes including a metallic element secured to said other tongue:section of said one tongue extending away from the bent-over tonguesection.

6. In an electron space discharge device housed in a sealed tubularenvelope: an assembly of electrodes extending longitudinally generallyparallel to a common axis including a filamentary cathode and at leasttwo additional electrodes and a tubular anode of sheet metal surroundingall said electrodes; two spaced, generally flat sheet-like insulatingspacers extending transversely to said axis and having two transverselydisposed rows of spacer openings holding the opposite ends of saidelectrodes in their operatively spaced positions; each of said two rowsof spacer openings including a common central spacer opening and twooutward spacer openings spaced by a distance from said central spaceropening; said spacer having four peripherally displaced spacerprojections aligned adjacent said four outward spacer openings andengaging the inner surface of the envelope for spacing said assemblyfrom the envelope; each peripheral edge of said spacers having at leasttwo spaced retainer recesses each of small depth and relatively largewidth and positioned between two spacer projections thereof; each of theopposite ends of said tubular anode having at least two junction sheettongues extending from the edge thereof and interlockingly engaging andinterfitting the two spaced recesses of said two spacersfor securingsaid two spacersto said anode and joining them and said electrodes intoa self-supporting electrode assembly, at

anode having two separate tongue sections; one" tongue section beingangularly bent over the spacer surface and the other tongue sectionextending away therefrom.

7. In a space discharge device asclaimed in claim 6, said assembly ofelectrodes'i ncluding a metallic element secured to said other tonguesection of said one tongue extending away from the bent-over tonguesection.

HERBERT R. JACO'BUS', JR. HAROLD L. LIPSCHULTZ.

REFERENCES CITED file of this patent:

Number 2350303 2355,083 2,402,797 2,433,410" 2,45%?{8'61' 2,464,241 f 2,16 1,272 23761940 2,486,829 The following references" are of record inthe 2,487159'2' Name Date Schade Feb. s, 1933 Rockwood Dec. 16, 194}Seeln Sept. 22, 1942 West May 30, 195151 Krim Aug. 8, 1944 Wood June 25,1946 Walkere't al. Dec. 30, 194? Wood -Jan. 25, 1949 Krim Mar. 15, 1949Sue'sholtz Mar; 15, 1949 Wood July 19, 1949 Nov. 1, 1949 Rishe ll Nov;8. 1949'

